1. Field of the Invention.
The invention of the present application relates to Fe-Ni based alloys having improved soft magnetic properties and containing nanocrystalline particles. The Fe-Ni based alloys of the present invention may be tailored to specific applications by varying the annealing conditions. The formation of the nanocrystalline phase is achieved without the addition of copper.
2. Description of the Prior Art
Materials exhibiting good soft magnetic properties (ferromagnetic properties) include certain crystalline alloys (such as Permalloys), certain amorphous metallic alloys (such as cobalt or iron based alloys) and more recently, certain alloys containing nanocrystalline particles. Each of the three types of alloys has particular advantages and disadvantages associated with their production, use and characteristics.
Since metallic glasses were first formed, researchers have been looking for new compositions which possess improved soft magnetic properties, such as low magnetostriction, low core loss, and high saturation induction in combination with thermal stability, and cost efficient production. Metallic glasses containing cobalt have the best magnetic properties, but are expensive. Fe and Fe-Ni based soft magnetic alloys are much cheaper to produce because the components are cheaper, but display slightly less desirable magnetic properties. Thus, much research has centered around developing an Fe or Fe-Ni based soft magnetic alloy with improved magnetic characteristics.
Amorphous metallic metals are produced from alloys, and cooled at a very fast rate so that no crystalline structure forms. The rapid cooling prevents the formation of long range order within the metal, and gives the resulting metal its amorphous structure. The lack of long range order and defects such as grain boundaries gives the resulting amorphous metal good soft magnetic properties such as good dc properties and low core loss as well as good ductility.
Permalloys, Ni-based alloys, are cast into ingots. The ingots are then rolled into sheets, which can be worked into the desired shape. Permalloys display crystalline structure throughout the composition, and show low saturation induction and small magnetostrictions, but lose their soft magnetic properties when subjected to plastic deformation.
U.S. Pat. No. 4,881,989 discloses soft magnetic materials formed from Fe-Co or Fe-Ni base alloys containing 0.1 to 3.0 atomic percent Cu, and 0.1-30 atomic percent of at least one element from the group Nb, W, Ta, Zr, Hf, Ti and Mo, and containing crystallites with an average particle size of 100 nm or less. The Fe-Ni and Fe-Co based soft magnetic alloys disclosed in U.S. Pat. No. 4,881,989 exhibit good magnetic properties, but require the addition of copper which is not soluble in Fe in order to provide nucleation sites for the formation of nanocrystallites.
U.S. Pat. No. 4,985,089 discloses Fe-Ni and Fe-Co based soft magnetic alloy powders having 0.1 to 3 atomic % Cu, 0.1 to 30 atomic % of an element chosen from Nb, W, Ta, Zr, Hf, Ti, and Mo; 0 to 10 atomic % of an element chosen from V, Cr, Mn, A1, elements in the platinum group, Sc, Y, rare earth elements, Au, Zn, Sn, and Re; and 0 to 10 atomic % of an element chosen from C, Ge, P, Ga, Sb, In, Be, and As. The alloys have fine crystalline particles with an average particle size of 500 A or less, a bcc Fe-based crystal structure and require the addition of Cu.
Studies on the formation of crystallites in Fe and Fe-Ni based alloy compositions without the addition of Cu have been previously reported. For example, Magnetic Properties of Glassy (Fe-Ni).sub.86 B.sub.14 Alloys, R. Hasegawa, Journal De Physique, Colloque C8, supplement 8, Tome 41, pages 701-704, 1980 reports dual crystallization events having separate crystallization and Curie temperatures for several (Fe-Ni).sub.86 B.sub.14 alloys.
Dual crystallization events for Fe.sub.43-84 Ni.sub.0-41 Mo.sub.2-8.5 B.sub.10-15 are reported in Effect of Composition in (Fe, Ni, Cr,) (P, B) and (Fe, Ni, Mo)B Metallic Glasses, Antonione, Battezzati, Lucci, Riontino, Tabasso, Venturello, Journal De Physique, Colloque 8, supplement 8, Tome 41, pages 131-134, 1980.
Studies of the kinetics of the crystallization temperatures of Fe.sub.40 Ni.sub.38 Mo.sub.4 B.sub.18 are reported in Effect of Thermal Treatments Beyond T.sub.g on Crystallization Kinetics in Metallic Glasses, Antonione, Battezzati, Lucci, Riontino, Tabasso, Venturello, Proceedings of the Conference on Metallic Glasses: Science & Technology, vol. 2, pages 151-156, 1980.
TEM Studies of Kinetics of Crystallization of Three Fe-Ni Based Alloys, Ranganathan, Claus, Tiwari and Heimendahl, Proceedings of the Conference on Metallic Glasses, Science & Technology, Budapest 1980, vol. 2, pgs 327-333, discusses the kinetics of crystallization of three Fe-Ni based compositions.
Thermal Stability and Crystallization of Transition Metal-Boron Metallic Glasses, Kemeny, Vincze, Balogh, Granasy, Fogarassy, Hajdu, Svab, Proceedings of the Conference on Metallic Glasses, Science & Technology, Budapest 1980, vol. 2, pg 231-238, discusses the structure of the crystalline phases of (Fe-Ni)B and (Fe-Co)B amorphous alloys.
However, these studies concentrated on the kinetics of crystallization, and wholly failed to recognize or consider the soft magnetic properties of the resulting alloys, which can be achieved via post casting treatment of the alloy, or a process capable of optimizing said soft magnetic properties.
Further, the cited patents require the copper to seed nanocrystalline growth, and report a nanocrystalline phase with a bcc crystalline structure.